The invention pertains to process for handling disk-like objects using a chuck.
The invention further pertains to a chuck for disk-like objects, with which disk-like objects can be held during treatment steps and can be caused to rotate and with which the process of the invention can be carried out. In particular, such chucks are intended for holding (silicon) wafers and rotating them while they are being treated, e.g., etched, polished, and washed.
Chucks of this type come in basically two designs. In the side of the chuck facing toward the object, one design has pins (U.S. Pat. No. 4,903,717 and U.S. Pat. No. 5,513,668) by which the disk-like objects are laterally supported, while they are held against the chuck under the action of the gas emerging from a ring nozzle, primarily according to the Bernoulli principle. In another design of such chucks for disk-like objects (WO 97/03457), such pins are not provided since the object is held against the chuck by an underpressure that is applied to, e.g., ring-shaped projections on the chuck surface facing the object.
Up until now, the mounting of a disk-like object, especially a (silicon) wafer, on a chuck and removal of the object therefrom have been laborious processes. The reason for this is that in the case of chucks that are equipped with pins there is only a very small gap between the object and the surface of the chuck facing it, and in chucks against which objects are held by means of underpressure there is virtually no gap. Thus, up until now it has not been possible to use the known spoons or forks with which disk-like objects, especially silicon wafers, can be grasped from below in order to mount them onto the chuck and remove them therefrom. Such spoons are, however, used to remove wafers from support trays in supply containers (carrier boxes) and to put them back into these boxes.
To solve this problem, various gripping devices have been proposed for disk-like objects (wafers). For example, see the gripper shown in AT 000 640 U1 or WO 95/11518. Such grippers work adequately, especially if there is a gap (albeit a small one) between the disk-like object and the chuck, but they require that, both to mount the disk-like object and to remove it, a second gripper (spoon) be used to empty/fill the support trays in supply containers.